A gap junction is known as a cell-to-cell contact site on a cell surface. The present inventors had discovered that carbenoxolone, a glycyrrhetinic acid derivative, which is a gap junction inhibitor, inhibits the release of excess glutamate from activated microglia and established that a gap junction inhibitor can be used for treating nervous system diseases. (Patent reference 1)
Furthermore, a gap junction is known to be involved in a variety of transmissions of stimulation such that novel junction inhibitors are useful for various research applications.    Patent reference 1: International publication WO 2007/No. 088712 pamphlet.